Our estimates show a pandemic with Rt values estimated mainly very close to 1. This is reflected in infection incidence which has remained reasonably constant for over one month and is now starting to feed through to the deaths, which are hitting a plateau.
Our change to the vaccine efficacy assumptions has resulted in a downward revision of infection attack rates. Whereas previously we were estimating 81% and 69% for the 5-14 and 15-24 year-olds respectively, these have been revised down by around 10% to 70% and 59% respectively.
Plots of the IFR over time show that we are currently estimating a decreasing IFR in all age groups with the most steep fall in the younger age groups. Following this drop, the overall IFR is 0.24% (0.23%–0.26%), highest in the over-75s at 3.4% (3.1%–3.7%), similar to that estimated last week.
For context, in addition to the data used here, the number of reported new positive cases (by date of specimen) is increasing. As a caveat to this, trends in the number of reported cases are highly dependent on the volume and targeting of testing, the public’s testing behaviour and significant reporting delays, and therefore are difficult to interpret. Overall, there have now been 9.0million positive tests in England, which we estimate to have been generated from 22.7million cumulative infections. This would suggest that almost 40% of infections have been identified. This seems plausible if a little high considering the low ascertainment rates of the first wave. In contrast to the cases, the admissions to hospitals have been falling in number, though there is now evidence that this is flattening out. The prevalence of infection, as estimated by the ONS Coronavirus Infection Survey, remains stable around 1.65% in England, while showing some slight increasing trends in some regions. As yet, infection with the omicron variant is not sufficiently widespread to greatly influence these results. It is anticipated that this will not be the case for much longer.
Real-time tracking of an epidemic, as data accumulate over time, is an essential component of a public health response to a new outbreak. A team of statistical modellers at the MRC Biostatistics Unit (BSU), University of Cambridge, are working to provide regular now-casts and forecasts of COVID-19 infections and deaths. This information feeds directly to the SAGE sub-group, Scientific Pandemic Influenza sub-group on Modelling (SPI-M), and to regional Public Health England (PHE) teams.
We fit a transmission model (Birrell et al. 2020) to a number of data sources (see ‘Data Sources’), to reconstruct the number of new COVID-19 infections over time in different age groups and NHS regions, estimate a measure of ongoing transmission and predict the number of new COVID-19 deaths.
We use:
Data are stratified into eight age groups: <1, 1-4, 5-14, 15-24, 25-44, 45-64, 65-74, 75+, and the NHS England regions (North East and Yorkshire, North West, Midlands, East of England, London, South East, South West).
Value of \(R_t\), the average number of secondary infections due to a typical infection today.
The percentage of a given group that has been infected.
NB: negative growth rates are rates of decline. Values are daily changes.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 0.00 | -0.01 | 0.00 |
| East of England | -0.02 | -0.04 | 0.00 |
| East Midlands | -0.03 | -0.04 | -0.01 |
| London | 0.01 | 0.00 | 0.03 |
| North East | 0.00 | -0.02 | 0.02 |
| North West | -0.01 | -0.03 | 0.01 |
| South East | 0.00 | -0.02 | 0.01 |
| South West | -0.01 | -0.03 | 0.01 |
| West Midlands | -0.02 | -0.04 | 0.00 |
| Yorkshire and The Humber | -0.01 | -0.03 | 0.01 |
Halving times in days, if a region shows growth than value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 223.22 | 75.58 | NA |
| East of England | 33.01 | 17.87 | 175.34 |
| East Midlands | 26.12 | 15.13 | 77.57 |
| London | NA | NA | NA |
| North East | NA | 41.91 | NA |
| North West | 60.15 | 20.99 | NA |
| South East | 304.23 | 38.83 | NA |
| South West | 64.88 | 23.70 | NA |
| West Midlands | 33.97 | 18.09 | 275.60 |
| Yorkshire and The Humber | 61.64 | 24.74 | NA |
Doubling times in days, if a region shows decline then the value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | NA | 161.27 | NA |
| East of England | NA | NA | NA |
| East Midlands | NA | NA | NA |
| London | 46.47 | 24.01 | 341 |
| North East | 1645.51 | 45.41 | NA |
| North West | NA | 66.81 | NA |
| South East | NA | 49.25 | NA |
| South West | NA | 125.77 | NA |
| West Midlands | NA | NA | NA |
| Yorkshire and The Humber | NA | 138.54 | NA |
NB: negative growth rates are rates of decline. Values are daily changes.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 0.00 | -0.01 | 0.00 |
| East of England | -0.01 | -0.02 | 0.00 |
| East Midlands | -0.01 | -0.03 | 0.00 |
| London | 0.02 | 0.00 | 0.03 |
| North East | 0.01 | -0.01 | 0.02 |
| North West | -0.01 | -0.03 | 0.00 |
| South East | 0.00 | -0.01 | 0.02 |
| South West | -0.01 | -0.02 | 0.01 |
| West Midlands | -0.01 | -0.03 | 0.00 |
| Yorkshire and The Humber | -0.01 | -0.02 | 0.00 |
Halving times in days, if a region shows growth than value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | 217.14 | 81.54 | NA |
| East of England | 54.42 | 27.58 | NA |
| East Midlands | 48.63 | 26.44 | 7158.01 |
| London | NA | NA | NA |
| North East | NA | 79.98 | NA |
| North West | 53.64 | 25.70 | NA |
| South East | NA | 60.45 | NA |
| South West | 99.47 | 34.23 | NA |
| West Midlands | 47.46 | 25.39 | 1119.59 |
| Yorkshire and The Humber | 65.92 | 29.21 | NA |
Doubling times in days, if a region shows decline then the value will be NA.
| Region | Median | 95% CrI (lower) | 95% CrI (upper) |
|---|---|---|---|
| England | NA | 280.49 | NA |
| East of England | NA | 871.57 | NA |
| East Midlands | NA | NA | NA |
| London | 41.71 | 22.69 | 220.64 |
| North East | 102.99 | 31.63 | NA |
| North West | NA | 157.00 | NA |
| South East | 811.08 | 43.08 | NA |
| South West | NA | 84.25 | NA |
| West Midlands | NA | NA | NA |
| Yorkshire and The Humber | NA | 181.49 | NA |
## The execution of the prevalence code block will proceed if
## prev.dat exists and this is TRUE
## it is not and external report and this is FALSE
The shaded areas show periods of national lockdown, the green lines the dates (once confirmed) of the steps in the roadmap in the UK Governement’s COVID-19 Response – Spring 2021, and the red line shows the date these results were produced (03 Dec).
The figure below shows the probability that \(R_t\) is greater than 1 (ie: the number of infections is growing) in each region over time. Clicking the regions in the legend allows lines to be added or removed from the figure.
Copyright © MRC Biostatistics Unit, University of Cambridge